This invention relates to a dust collector and, in particular to a dust collector for handling high temperature gases such as air containing fine particulate materials.
In many industrial processes high temperature air is generated that contains dust particles or the like that are environmentally unsafe and thus, cannot be released into the atmosphere. The air temperature in many cases, can exceed 1600xc2x0 F. and, as a consequence, can have a harmful effect on the component parts of most conventional dust collectors. At particular risk are the diaphragm valves used to control the flow of blowdown air used to dislodge dirt and dust from filter tubes contained in the collector unit. Among other things, these valves contain gaskets that fail when exposed to temperature at or about 450xc2x0 F. In order to protect the valves from high temperature, it has heretofore been the practice to place an orifice in the blow down tube in front of the valve. This allowed cool ambient air to be pulled into the tube by the negative pressure experienced by the blowdown tube during those periods when it is not in use. Although this method of protecting the diaphragm valves works well for temperatures below 1000xc2x0 F., it does not provide protection for the valves at the higher temperatures now being generated by many industrial processes.
Further problems are experienced by dust collectors at these higher temperatures. Many of the mating parts of the collector cannot accommodate the thermal deformation produced as the parts are heated to very high temperatures. Differences in the thermal coefficient of expansion of parts at high temperatures can cause failures when the joints between parts cannot accommodate the expansion produced at these high temperatures.
It is therefore a primary object of the present invention to improve dust collectors.
It is a further object of the present invention to improve dust collectors that handle air or other gases at high temperatures and, in particular, temperatures above 500xc2x0 F. up to 1500xc2x0 F.
It is a still further object of the present invention to protect the valves for introducing blowdown air into a dust collector from high internal temperatures experienced by the collector unit.
Another object of the present invention is to provide a dust collector that can accommodate thermal expansion of parts produced at high temperatures.
These and other objects of the present invention are attained in a high temperature dust collector that includes a filter housing containing ceramic filter tubes that empty into a clean air plenum mounted on top of the housing. Horizontally disposed blowdown tubes are mounted in rows within the plenum chamber over the filter tubes and a jet of cleaning air is periodically introduced into each of the filter tubes to dislodge dirt and dust collected on the outside of the filter tubes. Diaphragm valves for controlling the flow of compressed air to the blowdown tubes are located outside of and adjacent to the plenum chamber. The valves are connected to the blowdown tubes by inlet pipes that are arranged to pass through a cooling unit that is adapted to pass cool ambient air around the pipes. The cooling unit consists of a first vertically disposed rear heat shield mounted adjacent to the plenum chamber and a front heat shield that is spaced apart from the rear heat shield. The shields are flat plates that combine to both physically shield the valves from heat produced within the collector and to produce a chimney effect which produces a natural flow of ambient air over the inlet pipes when the pipes are conductively heated. The pipes are equipped with heat transfer fins which helps to dissipate the heat of conduction from the pipes into the flow of ambient air.
Critical joints within the collector are further adapted to accommodate expansion of cojoined parts without causing damage that might normally occur at high temperatures.